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January Mid/long Range Winter Discussion


Wow

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Lots of good mets gave great evidence as to why this winter should be above average for snowfall in our area. You went against the evidence because your always pessimistic about snow here. Congrats.

 

So far, lots of good mets 0, Packbacker 1.  Let's not take a victory lap just yet, though.

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Thanks for the explanations again guys.  Sounds like we need either one of two things 1. Get a stronger PNA to bend the northern stream south, stop the zonal pacific flow thus bringing colder air in from the west (sounds like moving the aleutian low further west is part of that), or 2. Get the PV further east to form I guess is what is called the 50/50 low, underneath the blocking, causing cold air intrusion into the east.  If someone could explain confluence to me very briefly I'd appreciate it.  Just trying to learn as much as I can.  Thanks!

 

Seems like all this blocking is playing into the 1998 analog pretty well since that year had a solid -AO, but turned out warm and snowless for CLT.  Starting to wish for the +PNA/-EPO/+AO combo we had the last two years!

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The clipper dropping down in the 12-13th period has me interested. If it can dig enough we could see a nice 1-2" snow from it across the area. These usually aren't handled well until within 72 hours, from my experience, so it's worth keeping an eye on that piece of energy to see what models do with it as we get closer. They've been quite inconsistent with a different look about every time.

EDIT: Here is what the Canadian shows at hour 120, vort dropping nicely and a little southern energy around too. Wouldn't be hard to get a few inches if it digs enough.

post-2321-0-89700000-1452186135_thumb.pn

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Lots of good mets gave great evidence as to why this winter should be above average for snowfall in our area. You went against the evidence because your always pessimistic about snow here. Congrats.

It takes one system in a strong El Niño year to put most areas above average. That's not saying much.
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The clipper dropping down in the 12-13th period has me interested. If it can dig enough we could see a nice 1-2" snow from it across the area. These usually aren't handled well until within 72 hours, from my experience, so it's worth keeping an eye on that piece of energy to see what models do with it as we get closer. They've been quite inconsistent with a different look about every time.

EDIT: Here is what the Canadian shows at hour 120, vort dropping nicely and a little southern energy around too. Wouldn't be hard to get a few inches if it digs enough.

Need to sharpen up that PNA a little bit. :)

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The clipper dropping down in the 12-13th period has me interested. If it can dig enough we could see a nice 1-2" snow from it across the area. These usually aren't handled well until within 72 hours, from my experience, so it's worth keeping an eye on that piece of energy to see what models do with it as we get closer. They've been quite inconsistent with a different look about every time.

EDIT: Here is what the Canadian shows at hour 120, vort dropping nicely and a little southern energy around too. Wouldn't be hard to get a few inches if it digs enough.

 

 

Need to sharpen up that PNA a little bit. :)

 

I agree, clipper could have legs.   Let's see if the Euro can dig that heck out of that...back in Oct/Nov it did that a couple of times.

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that is one for the books. normally that would have us crying with joy and yet is still gives rain to most of us. this winter is a lesson in pain so far.

The models in the long range show as many lows cutting with a -NAO and blocking as they do taking an offshore track in a hostile pattern, believe me you won't have to worry about a cutter if that block is there

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Need to sharpen up that PNA a little bit. :)

Yep at least it has some potential to produce if that happens. Euro has been close, off and on the past few days. I have a feeling this might be one of those 72 hour systems where models start picking up on how sharp our ridging is and how much it digs.

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I like the 13-16 period, still.  I'm not off that bandwagon yet.

 

You are not wrong to do that.  Models tend to rush transition periods and that includes NAO or AO drops or rises.  Operational models are really not terribly useful past 120 hours.  I know people want fantasy snow; but fantasy snow doesn't count in the tally when the winter is over.  We are not even truly in range of the most favorable period for these operational models (Euro included).

 

That being said, the Ensembles have been very suppressing for that period as well.  Perhaps we can sneak a northern stream event.

 

Nothing is going to cut with this.

ecmwf-ens_z500a_nhem_8.png

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The models in the long range show as many lows cutting with a -NAO and blocking as they do taking an offshore track in a hostile pattern, believe me you won't have to worry about a cutter if that block is there

I do believe you because even on a op run I feel like it should show that low heading ENE with that block.  That tells me it must be out to lunch.  The only thing I feel good about is this block coming to fruition. 

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The models in the long range show as many lows cutting with a -NAO and blocking as they do taking an offshore track in a hostile pattern, believe me you won't have to worry about a cutter if that block is there

 

Is it the -NAO block (higher heights) that blocks storms from cutting or is it the PV underneath?  It seems on the models we're going to have the block/-NAO but the PV too far west is allowing the storms to still cutt to the lakes.  Or are you saying with that ridging over greenland there should be no cutters regardless of where the PV is? Thanks.

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Is it the -NAO block (higher heights) that blocks storms from cutting or is it the PV underneath? It seems on the models we're going to have the block/-NAO but the PV too far west is allowing the storms to still cutt to the lakes. Or are you saying with that ridging over greenland there should be no cutters regardless of where the PV is? Thanks.

Storms can cut in a bastardized -NAO which technically isn't a -NAO at all. That shows up very very late in the GFS run where high splits off and goes over central Canada as a blocking high. In those instances storms can cut but that is not a -NAO if you ask me because the high is so far west that your heights over Greenland are probably near normal hence your NAO is neutral at best. 336 hours at 500mb is the pattern I'm describing, that may be considered a -NAO by some but not me. The pattern at 210 hours is a true -NAO and one where a storm is highly unlikely to cut

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We haven't had a blocky looking pattern like this in several years.....I'm not too worried about the fine details at this point. The big picture is favorable for winter weather. If we could scrape out a couple of snows the last few years with crappy patterns, I'm excited to see what transpires during the coming weeks.....

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You are not wrong to do that.  Models tend to rush transition periods and that includes NAO or AO drops or rises.  Operational models are really not terribly useful past 120 hours.  I know people want fantasy snow; but fantasy snow doesn't count in the tally when the winter is over.  We are not even truly in range of the most favorable period for these operational models (Euro included).

 

That being said, the Ensembles have been very suppressing for that period as well.  Perhaps we can sneak a northern stream event.

 

Nothing is going to cut with this.

 

I agree.  Give me that look and the biggest concern is the southern stream feeling the meat grinder.  I don't really understand the models though. It seems given that look the models would know it can't send a low to the lakes. 

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Hello everyone.

Don't get a chance to post here a lot but I was passing through and saw a couple of good points being made by Cold Rain and NC Rain.

Not all -NAO's are created equal and they are getting at is that there are two types of -NAO, west and east based. Basically east based means that the positive anomalies set up east of Greenland while the west based has the positive anomalies setting up between Greenland and Hudson Bay.

The two advantages of a west based NAO is that you get better confluence over SE Canada locking in the cold high over the north. The second is you force the main negative anomalies over the northwest Atlantic (the 50/50 low) with prevents storms from cutting north until off the East Coast.

What we have coming up seems to be somewhere in the middle where the + anomalies are centered right around Greenland which can leave a window for storms to cut. Now the strength of block may play a part in this too but I would really like to see the block move a little further west. I believe some of the ensembles and deterministic models have shown this in the longer ranges.

This doesn't mean that we can't get snow with the pattern as modeled it means we need the correct timing between waves within the northern and southern streams.

Here is a good article from the NC State climate office. Just scroll down to the bottom to get to the part on west vs east based NAO's.

 

https://climate.ncsu.edu/climate/patterns/NAO.html

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Hello everyone.

Don't get a chance to post here a lot but I was passing through and saw a couple of good points being made by Cold Rain and NC Rain.

Not all -NAO's are created equal and they are getting at is that there are two types of -NAO, west and east based. Basically east based means that the positive anomalies set up east of Greenland while the west based has the positive anomalies setting up between Greenland and Hudson Bay.

The two advantages of a west based NAO is that you get better confluence over SE Canada locking in the cold high over the north. The second is you force the main negative anomalies over the northwest Atlantic (the 50/50 low) with prevents storms from cutting north until off the East Coast.

What we have coming up seems to be somewhere in the middle where the + anomalies are centered right around Greenland which can leave a window for storms to cut. Now the strength of block may play a part in this too but I would really like to see the block move a little further west. I believe some of the ensembles and deterministic models have shown this in the longer ranges.

This doesn't mean that we can't get snow with the pattern as modeled it means we need the correct timing between waves within the northern and southern streams.

Here is a good article from the NC State climate office. Just scroll down to the bottom to get to the part on west vs east based NAO's.

 

https://climate.ncsu.edu/climate/patterns/NAO.html

 

 

Just for the sake of discussion then, looking at this map on the GFS, we have what seems to be a very stout west based -NAO and a finely placed 50/50 low which as mentioned, should create nice confluence in the east, thus making it cold in the east.  My question is why does the temp anomaly map for this time period show warm up and down the east coast? 

 

TcNZLo9.png

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Just for the sake of discussion then, looking at this map on the GFS, we have what seems to be a very stout west based -NAO and a finely placed 50/50 low which as mentioned, should create nice confluence in the east, thus making it cold in the east.  My question is why does the temp anomaly map for this time period show warm up and down the east coast? 

 

TcNZLo9.png

maybe because the flow is SW over the East coast.  block yes but that is a warm direction. just my 2 cents.

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Just for the sake of discussion then, looking at this map on the GFS, we have what seems to be a very stout west based -NAO and a finely placed 50/50 low which as mentioned, should create nice confluence in the east, thus making it cold in the east.  My question is why does the temp anomaly map for this time period show warm up and down the east coast? 

 

TcNZLo9.png

 

I will try to kill two birds with one stone here.  You asked about confluence earlier.  (Forgive the drawing).

 

The Greenland Block/-NAO is very impressive.  But look where the PV is centered -- just north of MN.  There will be some impressive cold in that area, if that setup occurs.  I have drawn arrows that represent the flow at 500mb.  Where the arrows come together (on the west side of the PV), you have confluence.  Air converges up there and sinks near the ground, which promotes higher pressure.  The reverse is true where the arrows diverge (notice where that is -- unfortunately, right in the wrong place, up in the NE).

 

You also have a PNA ridge that is a bit too far west, and you have Packbacker's favorite feature, the SW trough.  The flow is out of the SW over the SE (which is not always a bad thing), and you have no real mechanism to transport or maintain a strong high pressure, delivering cold air, toward the east.  You need the PV to be east of it's location in that map.  And preferably the PNA ridge.  That would bring the confluence zone into a better spot.

 

I personally don't care for this snapshot, as it relates to our winter weather chances.  That said, it has the potential to evolve into a much more favorable setup.  Fingers crossed.....!

 

 

post-987-0-57635100-1452192362_thumb.jpg

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